8 Kingdoms is a 3D turn based fantasy strategy game. Build empires and conquer enemy kingdoms. I came across it in the Ubuntu forums where the poster suggested the graphics were not that great. Well, the graphics look pretty good to me. In fact I quite like the plastic-like model style. It gives the game an interesting look and feel. The game is at version 1.0 so is fully playable. :-)
The map is hex based which also intrigues me. I always find hex more fascinating than boring square grids. There is only a Windows installer and a tar.gz available for download, so non-Windows players will probably have to compile it themselves.
Keeping on the strategy theme, I came across a game I'd lost the link for a while back. Legacy of Magic is a very promising looking fantasy war game. The homepage is a development blog although there has been no update since November 2006 so I'm going to email the author to see how he is getting on. It would be a shame for such a nice looking game to cease development.
Another upcoming open source strategy game seems to have lost it's way a little - the Galaxy Mage website is down [so that link won't work] but the code is always available from it's project page. The last code change was only a couple of months ago so hopefully the website will be back up soon and work resumed.
There's an interesting update on the Allacrost website regarding development. Basically they tackled the major architectural hurdles in the 0.2.0 release - the rather nice consequence of which is there will be much less time before the next release. :-D
Also the Egoboo Resurrection project released version 2.3.8 of their continuation efforts for this classic open source RPG game. It introduces new levels and bug fixes, but still is only being built for Windows although the game has strong Linux roots so surely will still be compilable should somebody take it on. I think they just don't have Linux expertise amongst the development group at the moment so head on over there if you think you can help out.
Not quite open source games, but I found this open source Java virtual PC rather fascinating and the 3 demo pages (1, 2, 3) have it running DOS (FreeDOS maybe?) loaded with several of the classic games of the DOS era such as Prince of Persia and Lemmings. Quite a nostalgic way to pass a few minutes of time for the elder gamers amongst us. Anyway, a quick reminder to help you get started: